Acute kidney injury (AKI) following non-cardiac surgery is common and has substantial health impact. Preclinical and clinical studies examining the influence of sex on AKI have yielded conflicting results, although they typically do not account for age-related changes. The objective of our study was to determine the association of age and sex groups on postoperative AKI. We hypothesized that younger females would display lower risk of postoperative AKI than males of similar age, and the protection would be lost in older females.


This was a multicenter retrospective cohort study across 46 institutions between 2013-2019. Participants included adult inpatients without pre-existing end-stage kidney disease undergoing index major non-cardiac, non-kidney/urologic surgeries. Our primary exposure was age and sex groups defined as females ≤50 years, females >50 years, males ≤50 years, and males >50 years. Our primary outcome was development of AKI by Kidney Disease-Improving Global Outcomes serum creatinine criteria. Exploratory analyses included associations of ascending age groups and hormone replacement therapy home medications with postoperative AKI.


Among 390,382 patients, 25,809 (6.6%) developed postoperative AKI (females ≤50: 2190/58585 [3.7%]; females >50: 9320/144047 [6.5%]; males ≤50: 3289/55503 [5.9%]; males >50: 11010/132447 [8.3%]). When adjusted for AKI risk factors, compared to females under 50 (odds ratio 1), the odds of AKI was higher in females over 50 (odds ratio 1.51, 95% CI 1.43-1.59), males under 50 (odds ratio 1.90, 95% CI 1.79-2.01), and males over 50 (odds ratio 2.06, 95% CI 1.96-2.17).